The present invention relates to a method and an apparatus for forming a tire reinforcing layer either directly or indirectly on the outer peripheral surface of a rigid core having a circular outer contour.
A conventional method and apparatus for forming a tire reinforcing layer on the outer peripheral surface of a rigid core with a substantially toroidal shape are disclosed, for example, in JP-A-05-185533.
In this instance, a reinforcing element comprising a single cord is supported by a mounting head which is moved to one side, in the width direction, of the crown portion of a core which is slowly rotating and a leading end of the reinforcing element is then clamped by a clip. Subsequently, the mounting head is moved obliquely along the surface of the crown portion of the core to the other side thereof, so that the reinforcing element is fed from the mounting head and adhered onto the outer peripheral surface of the core as being inclined at a constant angle with respect to the equatorial line of the core. The reinforcing element is then cut by a cutter at a location which is spaced a predetermined distance from its leading edge. These steps are repeated so that the reinforcing elements are successively adhered to the outer peripheral surface of the core in parallel with each other to form a belt layer.
However, in such conventional method and apparatus for forming the belt layer, since the reinforcing element to be adhered to the outer peripheral surface of the core is comprised of a single thin cord, there is a problem that a number of adhering operations of the reinforcing element are required to form a belt layer so that the operational efficiency is low.
Moreover, since the adhesion of the reinforcing element is performed by moving the mounting head in a direction in which the reinforcing member is adhered, there is a problem that, when the reinforcing element assumes a small inclination angle relative to the equatorial line of the core, or when the extending direction of the reinforcing element approaches the equatorial line of the core, it is necessary to move the mounting head over a relatively long distance which corresponds to the length of the reinforcing element to be adhered, thereby further lowering the operational efficiency.
It is an object of the present invention to provide a method and an apparatus for forming a tire reinforcing layer with an improved efficiency, either directly or indirectly on the outer peripheral surface of a rigid core having a circular outer contour.
The present invention provides a method for forming a tire reinforcing layer, which comprises the steps of: transferring a strip, which is comprised of a plurality of rubber-coated cords extending in parallel with each other, to a location adjacent to a rigid core having a circular outer contour, and cutting the strip into a predetermined length to form a ribbon pieces; transferring the ribbon piece onto an outer peripheral surface of the rigid core and adhering the ribbon piece to said outer peripheral surface as being inclined with reference to an equatorial line of the rigid core by a predetermined angle; and rotating the rigid core about a center axis thereof, by an angle which corresponds to the length of the ribbon piece in the circumferential direction; said steps being repeated so that the ribbon pieces are successively adhered to the outer peripheral surface of the rigid core while side edges of adjacent ribbon pieces are brought into close contact with each other.
The present invention also provides an apparatus for forming a tire reinforcing layer, which comprises: transferring and cutting means for transferring a strip, which is comprised of a plurality of rubber-coated cords extending in parallel with each other, to a location adjacent to a rigid core having a circular outer contour, and cutting the strip into a predetermined length to form a ribbon piece; transferring and adhering means for transferring the ribbon piece onto an outer peripheral surface of the rigid core and adhering the ribbon piece to said outer peripheral surface as being inclined with reference to an equatorial line of the rigid core by a predetermined angle; and rotating means for rotating the rigid core about a center axis thereof, by an angle which corresponds to the length of the ribbon piece in the circumferential direction.
According to the present invention, first of all, with the transferring and cutting means, a strip is transferred to a location adjacent to a rigid core having a circular outer contour, and is cut into a predetermined length to form a ribbon piece. Subsequently, with the transferring and adhering means, the ribbon piece is transferred onto an outer peripheral surface of the rigid core and adhering the ribbon piece to the outer peripheral surface as being inclined with reference to an equatorial line of the rigid core by a predetermined angle. Thereafter, with the rotating means, the rigid core is rotated about a center axis thereof, by an angle which corresponds to the length of the ribbon piece in the circumferential direction.
In this instance, the ribbon piece has a structure in which a plurality of cords are coated by rubber. Thus, a plurality of cords can be simultaneously set by one adhering operation of the ribbon piece, thereby reducing the number of adhering operations in forming a tire reinforcing layer and significantly improving the operating efficiency.
Moreover, the ribbon piece is cut from the strip at a location which is adjacent to the rigid core, so that the transfer distance required for the ribbon piece when it is to be adhered onto the rigid core can be sufficiently reduced, irrespective of the inclination angle of the cords relative to the equatorial line of the rigid core. From such a point also, it is possible to improve the operational efficiency upon formation of the tire reinforcing layer.
In the above-mentioned apparatus, it is preferred that the transferring and adhering means is comprised of magnetic or vacuum attracting elements for attracting and holding at least both end portions of the ribbon piece, and a moving mechanism for moving the magnetic or vacuum attracting elements. It is further preferred that the moving mechanism is comprised of manipulators the number of which is the same as the number of the magnetic or vacuum attracting elements such that the magnetic or vacuum attracting elements are connected to hands of the respective manipulators.
The former arrangement is simple in structure and ensures that the ribbon piece is positively held, transferred and adhered, and the latter arrangement is capable of simply and readily coping with changes to the rigid core in terms of the shape and dimension of the outer peripheral surface.
In the apparatus according to the present invention, the transferring and adhering means may be comprised of magnetic or vacuum attracting elements for attracting and holding at least both end portions of the ribbon piece, a press mechanism for urging the magnetic or vacuum attracting elements onto the outer peripheral surface of the rigid core with a substantially uniform force, and a moving mechanism for moving the press mechanism.
With such an arrangement, it is possible to urge each regions of the ribbon pieces onto the outer peripheral surface of the rigid core by a substantially uniform force under the deformation of the press mechanism, irrespective of the shape and dimension of the outer peripheral surface of the rigid core, or adhering orientation of the ribbon piece on that outer peripheral surface. Moreover, by using only one press mechanism, complicated controls with respect to the locations, moving amounts, etc., of a plurality of attracting elements are unnecessary, besides that the operating speed can be increased.
Preferably, the press mechanism is comprised of a pair of levers of the same length, having respective one ends which are hinge-connected to each other. The other end of each lever is connected to one ends of a pair of lever yokes of the same length. The other ends of the yoke levers are connected to a leaf spring which extends linearly in a horizontal plane, such that the pair of levers and the pairs of lever yokes are under predetermined opening. The magnetic or vacuum attracting elements are then secured to the leaf spring of the press mechanism. With such an arrangement, the press mechanism functions in the same manner as automobile wipers and realizes uniform urging force for the ribbon piece.
When the pairs of yoke levers are provided in multiple stages, it is readily possible to increase the number of attracting elements. Also, when the moving mechanism for moving the press mechanism is formed as a manipulator, it is possible to reduce the facility cost, to further simplify the operation and control, and to further increase the operational speed.